An MRI can be oversensitive

I am a 63-year-old distance runner. In 2004 I sustained what I believe to be a medial ligament strain and as a result of this I now have very stiff knee joints. My GP has referred me to an orthopaedic consultant and my intention is to request an MRI scan. Would this be the best way to determine my prognosis?

The older we become, the longer it takes to recover from injury. When you hurt yourself two years ago, you may have sustained an injury to one of the menisci (the cartilage shock absorbers between the thigh bone and the shin bone). The stiffness that you report is part and parcel of the ageing process, and of lifelong running activities. After the many thousands of miles you have run, you may well have lost elasticity in your joints, and you probably take longer to get going than you used to.

Although many patients believe that an MRI is the ultimate diagnostic tool, paradoxically the better the orthopaedic surgeon, the lower the percentage of patients in whom an MRI is required. Accurate physical examination and history collection are, in experienced hands, the best detection kit: my colleagues and I only request MRIs if we have diagnostic doubts. An MRI can be oversensitive - for example, it may identify as abnormal things that are, instead, totally healthy - and at times may miss a lesion.

Therefore, the chances are that your surgeon will be able to formulate a diagnosis on the basis of clinical examination and simple radiographs. Be prepared, given your age, to learn that you have some degenerative joint disease in your knee joints. It is not a sentence to enforced immobility, just a chance to change the physical activity you undertake, and to integrate it with other modes of exercise, such as rowing, cycling, swimming, using the elliptical trainer or the stepper.

· Professor Maffulli is a consultant orthopaedic and sports injury surgeon at Keele University medical school. If you have a question for him, email fitness@theguardian.com